1. Field of the Invention
The present invention relates to an image pickup apparatus provided with an optical member drive mechanism for driving an optical member using a bending optical system, and a lens barrel including a bending photographic optical system comprised of a plurality of lens groups.
2. Description of the Related Art
Conventionally, a technique related to the above-mentioned type of image pickup apparatus has been disclosed in Japanese Patent Laid-Open Publication No. H11-271829.
More specifically, a camera (image pickup apparatus) disclosed in Japanese Patent Laid-Open Publication No. H11-271829 is provided with a one-sided cam ring open forward in an optical axis direction, and second and third group lenses are spring-urged toward the cam face of the cam ring, whereby the group lenses are drivingly controlled in the optical axis direction in accordance with a zooming operation.
Further, in the above-mentioned camera, in the case of collapsing the group lenses, a first group lens is retracted, with the second and third group lenses being partially held in contact with the body of the camera, whereby the group lenses are accommodated in the camera body after releasing the contact between the one-sided cam ring and the second and third group lenses. This realizes reduction of the thickness of the camera.
In the above-mentioned conventional technique, an optical system is formed as a photographic optical system having a 3-group configuration in which the first group lens and the second group lens are driven by a cam mechanism, and the third group lens is drivingly controlled by another drive source implemented e.g. by a stepper motor. In the case of collapsing the group lenses, the second group lens holding the third group lens is brought into contact with the camera body, and the first group lens is retracted into an accommodated position. In this case, space between the first group lens and the second group lens is reduced against spring force to whereby the reduction of the thickness is achieved.
However, in Japanese Patent Laid-Open Publication No. H11-271829, an optical system using a reflective optical element and a mechanism for retracting the reflective optical element for accommodation are not disclosed at all. In other words, the above-mentioned conventional technique is applicable only to a zoom optical system having low magnification, but not to an optical system using a reflective optical element compatible with high magnification.
As a lens barrel to be mounted on an image pickup apparatus, such as a digital camera, there has been known one provided with a photographic optical system of a bending type (hereinafter referred to as “the bending photographic optical system”) comprised of a plurality of lens groups. In the bending photographic optical system, it is not required to arrange a plurality of lens groups in a straight line, and therefore it is possible to reduce the total length of the optical system required in the optical axis direction, to thereby reduce the thickness of the image pickup apparatus.
As an image pickup apparatus having such a bending photographic optical system configured as above, there has been disclosed one in which a light flux having passed through an object-side lens group is bent e.g. by a prism through approximately 90 degrees to be guided toward another lens group (see Japanese Patent No. 4028721). In this image pickup apparatus, the lens groups and the prism are connected by a guide shaft, and the prism is moved from its retract position to its reflecting position in accordance with an operation for causing the lens groups to project from the image pickup apparatus, and is moved to its retract position in accordance with an operation for causing the lens groups to be accommodated in the image pickup apparatus.
As an image pickup apparatus having the bending photographic optical system, there has been disclosed one having a so-called extendable lens barrel mounted thereon (see Japanese Patent Laid-Open Publication No. 2006-259685). According to Japanese Patent Laid-Open Publication No. 2006-259685, in a shooting mode, a reflective optical element is placed in a position for bending light rays incident through an extended object-side lens group, while in a non-shooting mode, the object-side lens group is retracted into a space emptied by a shift of the reflective optical element into its retract position.
In general, as the distance of travel of a lens group is longer, zoom magnification becomes higher. However, in the image pickup apparatus disclosed in Japanese Patent No. 4028721, a distance over which the lens group is projectable is limited by the configuration of the guide shaft connecting between the lens groups and the prism. Therefore, the projectable distance of the prism can be increased e.g. by prolonging the guide shaft, but the width of the image pickup apparatus has to be increased so as to accommodate the long guide shaft, which makes it impossible to achieve reduction of the thickness of the image pickup apparatus and high zoom magnification at the same time.
Further, Japanese Patent Laid-Open Publication No. 2006-259685 has disclosed no specific configuration for moving the reflective optical element. Accordingly, the image pickup apparatus disclosed in Japanese Patent Laid-Open Publication No. 2006-259685 cannot achieve both the shift of the reflective optical element to its retract position and reception of the object-side lens group into the shooting position of the reflective optical element.
As described above, none of the image pickup apparatuses, including the ones disclosed in Japanese Patent No. 4028721 and Japanese Patent Laid-Open Publication No. 2006-259685, each of which employs the conventional bending photographic optical system, can achieve reduction of the thickness and high zoom magnification at the same time.